{"id":"GO-2026-6118","revision":null,"records":[{"revision":"74d89992abea4113a9d790eb294b347e","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-47427","aliases":[],"title":"GitHub MCP Server: Nil Pointer Dereference DoS in completion/complete Handler","description":"GitHub MCP Server is GitHub's official MCP Server. Prior to 1.1.0, the CompletionsHandler function in pkg/github/server.go accesses params.Ref without first checking whether it is nil, so a completion/complete request with a missing or empty ref field triggers a nil pointer dereference and a Go runtime panic; because the crash occurs before any authentication or token validation, any unauthenticated client able to send JSON-RPC messages can crash the server, resulting in a complete denial of service. 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This issue is fixed in version 1.1.0.","state":0,"publishedAt":"2026-07-28T16:18:14.853+00:00","modifiedAt":"2026-10-24T13:10:00.147+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://github.com/github/github-mcp-server/commit/c88d2ecdd3bb07f7bdd75296e3ee676febf14f58","https://github.com/github/github-mcp-server/pull/2502","https://github.com/github/github-mcp-server/releases/tag/v1.1.0","https://github.com/github/github-mcp-server/security/advisories/GHSA-w4q6-qw23-4rg7"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-47427","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-476"],"productCriteria":["cpe:2.3:a:github:mcp_server:*:*:*:*:*:*:*:*"],"sourceDates":{"published":"2026-07-28T16:18:14.853","lastModified":"2026-10-24T13:10:00.147"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-47427","identifiers":["CVE-2026-47427"]},"retained":false,"historicalAffected":[]},{"revision":"1e33729c1ad44945add736a860e9a9b6","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-w4q6-qw23-4rg7","aliases":["CVE-2026-47427","GO-2026-6118"],"title":"GitHub MCP Server has Nil Pointer Dereference DoS in completion/complete Handler","description":"### Summary\n\nA nil pointer dereference vulnerability in the GitHub MCP Server causes it to crash when receiving a malformed `completion/complete` request with missing or empty parameters. This allows any unauthenticated client to cause a complete denial of service.\n\n### Details\n\nThe `CompletionsHandler` function in `pkg/github/server.go:198` accesses `params.Ref` without checking if it's nil first. When a client sends a `completion/complete` request with a missing `ref` field, the handler dereferences nil and the Go runtime panics.\n\nThe crash occurs before any authentication or token validation, so even requests with fake tokens can trigger it.\n\n### PoC\n\nAfter completing the MCP initialization handshake, send either:\n\n**Empty params:**\n\n    {\"jsonrpc\":\"2.0\",\"id\":2,\"method\":\"completion/complete\",\"params\":{}}\n\n**Missing ref field:**\n\n    {\"jsonrpc\":\"2.0\",\"id\":2,\"method\":\"completion/complete\",\"params\":{\"argument\":{\"name\":\"x\",\"value\":\"y\"}}}\n\n**Result:**\n\n    panic: runtime error: invalid memory address or nil pointer dereference\n    goroutine 42 [running]:\n    github.com/github/github-mcp-server/pkg/github.NewMCPServer.CompletionsHandler.func1(...)\n        pkg/github/server.go:198 +0x24\n\n### Impact\n\nAny unauthenticated client that can send JSON-RPC messages to the server can crash it immediately. This is a complete denial of service - the panic is unrecoverable and kills the process.\n\nAutomated fuzzing with mcpsec found 108 crashes out of 925 test cases (11.7% crash rate).\n\n### Timeline\n\n- **Feb 21, 2026** - Initial report sent to opensource-security@github.com\n- **Mar 03, 2026** - Follow-up email sent, no response\n- **Mar 21, 2026** - Re-verified on v0.33.0, sent detailed report with PoC, no response\n- **Apr 06, 2026** - GHSA filed after 44 days without acknowledgment\n\n### Suggested Fix\n\n    func (s *Server) CompletionsHandler(ctx context.Context, params *mcp.CompleteParams) (*mcp.CompleteResult, error) {\n        if params == nil || params.Ref == nil {\n            return nil, fmt.Errorf(\"invalid request: missing ref parameter\")\n        }\n        // ... rest of handler\n    }","state":0,"publishedAt":"2026-07-28T14:35:10+00:00","modifiedAt":"2026-08-18T15:11:03.6625986+00:00","affected":[{"ecosystem":"Go","name":"github.com/github/github-mcp-server","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"1.1.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"HIGH"}],"references":["https://github.com/github/github-mcp-server/security/advisories/GHSA-w4q6-qw23-4rg7","https://github.com/github/github-mcp-server/pull/2502","https://github.com/github/github-mcp-server/commit/c88d2ecdd3bb07f7bdd75296e3ee676febf14f58","https://github.com/github/github-mcp-server","https://github.com/github/github-mcp-server/releases/tag/v1.1.0"],"sourceUrl":"https://github.com/advisories/GHSA-w4q6-qw23-4rg7","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-w4q6-qw23-4rg7","identifiers":["GHSA-w4q6-qw23-4rg7","CVE-2026-47427","GO-2026-6118"]},"retained":false,"historicalAffected":[]},{"revision":"ed6b48c74ac240e39d5c1c2da923384e","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GO-2026-6118","aliases":["CVE-2026-47427","GHSA-w4q6-qw23-4rg7"],"title":"GitHub MCP Server has Nil Pointer Dereference DoS in completion/complete Handler in github.com/github/github-mcp-server","description":"GitHub MCP Server has Nil Pointer Dereference DoS in completion/complete Handler in github.com/github/github-mcp-server","state":0,"publishedAt":"2026-08-18T14:32:29+00:00","modifiedAt":"2026-08-18T15:00:19.847206+00:00","affected":[{"ecosystem":"Go","name":"github.com/github/github-mcp-server","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"1.1.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://github.com/github/github-mcp-server/security/advisories/GHSA-w4q6-qw23-4rg7","https://github.com/github/github-mcp-server/commit/c88d2ecdd3bb07f7bdd75296e3ee676febf14f58","https://github.com/github/github-mcp-server/pull/2502","https://github.com/github/github-mcp-server/releases/tag/v1.1.0"],"sourceUrl":"https://osv.dev/vulnerability/GO-2026-6118","license":"OSV · upstream source license applies","key":"osv:GO-2026-6118","identifiers":["GO-2026-6118","CVE-2026-47427","GHSA-w4q6-qw23-4rg7"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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